Although absorbent articles, such as sanitary napkins or panty liners, have improved a lot the last years with respect to various features like protection and comfort in use, there is still a consumer need for further improvements in these two directions.
Indeed, there exists a real consumer need for absorbent articles, typically for feminine protection articles, having improved liquid handling properties, namely enhanced liquid distribution properties and a liquid holding and containing capacity high enough for use without consumer fears of leakage or staining especially after prolonged period of wearing time, yet which are thin and flexible, thereby offering enhanced fit and comfort.
Leakage of body fluids from the absorbent article typically occurs once the article becomes saturated with absorbed fluid. However in practice leakage of body fluids form the article can also often occur before saturation of the article is reached. Leakage causes staining of the support or associated garments and therefore frequent changing of the absorbent article is often necessary to prevent such staining. Leakage before saturation of the article can be typically caused by exuding body fluid contacting and temporarily saturating the top layers of absorbent material at a central area of the absorbent article, which then causes the body fluid to migrate by wicking or flowing across the upper surface of the article from the central area to the side edges thereof, typically the longitudinal side edges, but also the transverse side edges, before it has penetrated and/or fully diffused within the main bulk of the absorbent core. This effect can be also increased by the presence in absorbent articles of well known fluid acquisition/distribution layers in addition to the main absorbent core, which while on one hand improve the distribution of the absorbed body fluid across a greater surface area of the absorbent core, by also increasing its migration speed, can also bring the fluid more rapidly toward the edges of the absorbent article before it is fully absorbed in the absorbent core, hence potentially causing leakage. This can be also the case if a fluid acquisition/distribution layer is comprised in the absorbent article below the absorbent core, e.g. between the absorbent core and the backsheet. Fluid can in fact in certain conditions rapidly penetrate through the entire thickness of the absorbent core and, before being further absorbed and diffused within the core itself, can be received and spread by an underlying fluid acquisition/distribution layer. This may occur for example with modern, very thin absorbent cores typically constituted by a laminated structure of at least two fibrous layers with particles of absorbent gelling material comprised therebetween. Such structures have a great capacity of absorbing and retaining fluid, but owing to the relatively slow absorption mechanism of the absorbent gelling material particles, are typically advantageously associated to one or more fluid acquisition/distribution layers to promote and increase the diffusion of the fluid, and a more efficient subsequent absorption in the core.
Of course leakage can be also promoted by user's movements during wear which cause the absorbent article to be deformed and compressed, and possibly the fluid to be squeezed out of the core. Particularly for sanitary napkins, prevention of leakage, typically side leakage in the lateral direction, but also in the transverse direction, is of primary importance for users.
A known solution to the problem of leakage in absorbent articles such as sanitary napkins is for example described in patent application GB 2019727, disclosing a sanitary napkin provided with a barrier sheet which is wider than the garment facing surface of the absorbent core and which has longitudinal edge portions which cover the longitudinal sides and preferably also the side margins of the body facing surface of the absorbent core. This solution has however the disadvantage of a relatively complicated structure, especially for application to modern thin absorbent articles, also comprising wings. Moreover, the portions of the barrier sheet folded over part of the body facing surface of the absorbent core actually limit the surface area of the core which is available for direct fluid acquisition.
Alternative types of barriers against leakage in absorbent articles are also described in prior art, constituted for example by seal lines or areas made e.g. by embossing, melting or heat sealing, as disclosed in U.S. Pat. No. 5,275,591, or by application of a water impermeable hot melt adhesive in selected locations, as described in U.S. Pat. No. 4,718,898. All these solutions have the common disadvantage that in any case they create areas in the absorbent structure where absorption is actually inhibited.
Still a further approach to the problem of leakage, and more typically of side leakage in absorbent articles is the provision of physical barriers on the body facing surface of the absorbent article, such as raised elements, or alternatively cuffs or walls which are capable of standing upwards from the body facing surface of the absorbent article during wear. This type of self standing cuffs, preferably also provided with elastic elements, are described for example in U.S. Pat. Nos. 5,074,856, 5,490,847, 5,810,800. The drawbacks of physical barriers are in the rather cumbersome construction, also implying complex manufacturing processes, particularly when present in combination with other rather usual features in absorbent articles, such as for example side wings. They could also be improved for what concerns conformability and comfort in use.
EP 1013291 A1 discloses a hot melt adhesive with superabsorbent polymers. The resulting thermoplastic hot melt adhesive material can be used to provide additional absorption capacity to absorbent structures in absorbent articles, as well as to adhesively bond substrates in the absorbent article, i.e. as an absorbent construction adhesive. The thermoplastic absorbent hot melt adhesive material can be also applied in form of longitudinal and/or transverse edge stripes generically over the core or over the topsheet, in order to provide some sort of barrier effect to body fluids. However, the absorbent articles disclosed in EP 1013291 A1 present the disadvantage of a far less than optimal liquid handling capability, particularly they have a poor capacity of effectively diffuse and distribute the fluid, while at the same time preventing leakage.
It is therefore an object of the present invention to provide an absorbent article having an improved fluid handling capacity, i.e. being capable of effectively acquiring, distributing and absorbing fluid, at the same time minimizing the risk of edge leakage, particularly from the longitudinal side edges.
It is a further object of the present invention to provide an absorbent article that combines in a synergistic way the advantageous and unique characteristics of different materials such as traditional fibrous elements and layers and thermoplastic hot melt adhesive materials which are also absorbent by incorporating absorbent gelling materials.